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'Photoinhibition' in keywords Facet   Publication Year 1991  [X]
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1Author    Michel Havaux3, Murielle EylettersbRequires cookie*
 Title    Is the in vivo Photosystem I Function Resistant to Photoinhibition? An Answer from Photoacoustic and Far-Red Absorbance Measurements in Intact Leaves  
 Abstract    Preillumination o f intact pea leaves with a strong blue-green light o f 400 W m "2 markedly inhibited both photoacoustically monitored 0 2-evolution activity and PS II photochemistry as estimated from chlorophyll fluorescence measurements. The aim o f the present work was to examine, with the help o f the photoacoustic technique, whether this high-light treatment dete­ riorated the in vivo PS I function too. High-frequency photoacoustic measurements indicated that photochemical conversion o f far-red light energy in PS I was preserved (and even tran­ siently stimulated) whereas photochemical energy storage monitored in light exciting both PS I and PS II was markedly diminished. Low-frequency photoacoustic measurements of the Emerson enhancement showed a spectacular change in the PS II/PS I activity balance in favor o f PS I. It was also observed that the linear portion o f the saturation curve of the far-red light effect in the Emerson enhancement was not changed by the light treatment. Those results lead to the conclusion that, in contrast to PS II, the in vivo PS I photofunctioning was resistant to strong light stress, thus confirming previous suggestions derived from in vitro studies. Estima­ tion of the redox state of the PS I reaction center by leaf absorbance measurements at ca. 820 nm suggested that, under steady illum ination, a considerably larger fraction o f PS I cen­ ters were in the closed state in high-light pretreated leaves as compared to control leaves, pre­ sumably allowing passive adjustment o f the macroscopic quantum yield o f PS I photochemis­ try to the strongly reduced photochemical efficiency o f photoinhibited PS II. 
  Reference    Z. Naturforsch. 46c, 1038—1044 (1991); received M arch 25/June 21 1991 
  Published    1991 
  Keywords    Photosystem I, Photoacoustics, Photoinhibition 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-1038.pdf 
 Identifier    ZNC-1991-46c-1038 
 Volume    46